Link `std` statically in `rustc_driver`

compiler/rustc/src/main.rs

@@ -1,3 +1,6 @@
+// We need this feature as it changes `dylib` linking behavior and allows us to link to `rustc_driver`.
+#![feature(rustc_private)]
+
 // A note about jemalloc: rustc uses jemalloc when built for CI and
 // distribution. The obvious way to do this is with the `#[global_allocator]`
 // mechanism. However, for complicated reasons (see

compiler/rustc_metadata/src/dependency_format.rs

@@ -51,7 +51,7 @@
 //! Additionally, the algorithm is geared towards finding *any* solution rather
 //! than finding a number of solutions (there are normally quite a few).
 
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::def_id::CrateNum;
 use rustc_middle::bug;
 use rustc_middle::middle::dependency_format::{Dependencies, DependencyList, Linkage};
@@ -160,18 +160,43 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
         Linkage::Dynamic | Linkage::IncludedFromDylib => {}
     }
 
+    let all_dylibs = || {
+        tcx.crates(()).iter().filter(|&&cnum| {
+            !tcx.dep_kind(cnum).macros_only() && tcx.used_crate_source(cnum).dylib.is_some()
+        })
+    };
+
+    let mut upstream_in_dylibs = FxHashSet::default();
+
+    if tcx.features().rustc_private {
+        // We need this to prevent users of `rustc_driver` from linking dynamically to `std`
+        // which does not work as `std` is also statically linked into `rustc_driver`.
+
+        // Find all libraries statically linked to upstream dylibs.
+        for &cnum in all_dylibs() {
+            let deps = tcx.dylib_dependency_formats(cnum);
+            for &(depnum, style) in deps.iter() {
+                if let RequireStatic = style {
+                    upstream_in_dylibs.insert(depnum);
+                }
+            }
+        }
+    }
+
     let mut formats = FxHashMap::default();
 
     // Sweep all crates for found dylibs. Add all dylibs, as well as their
     // dependencies, ensuring there are no conflicts. The only valid case for a
     // dependency to be relied upon twice is for both cases to rely on a dylib.
-    for &cnum in tcx.crates(()).iter() {
-        if tcx.dep_kind(cnum).macros_only() {
+    for &cnum in all_dylibs() {
+        if upstream_in_dylibs.contains(&cnum) {
+            info!("skipping dylib: {}", tcx.crate_name(cnum));
+            // If this dylib is also available statically linked to another dylib
+            // we try to use that instead.
             continue;
         }
+
         let name = tcx.crate_name(cnum);
-        let src = tcx.used_crate_source(cnum);
-        if src.dylib.is_some() {
             info!("adding dylib: {}", name);
             add_library(tcx, cnum, RequireDynamic, &mut formats, &mut unavailable_as_static);
             let deps = tcx.dylib_dependency_formats(cnum);
@@ -180,7 +205,6 @@ fn calculate_type(tcx: TyCtxt<'_>, ty: CrateType) -> DependencyList {
                 add_library(tcx, depnum, style, &mut formats, &mut unavailable_as_static);
             }
         }
-    }
 
     // Collect what we've got so far in the return vector.
     let last_crate = tcx.crates(()).len();

src/bootstrap/src/bin/rustc.rs

@@ -89,6 +89,23 @@ fn main() {
         rustc_real
     };
 
+    // Get the name of the crate we're compiling, if any.
+    let crate_name = parse_value_from_args(&orig_args, "--crate-name");
+
+    // We want everything statically linked into `rustc_driver`, so remove `-C prefer-dynamic`
+    if crate_name == Some("rustc_driver") && stage != "0" {
+        // Remove `-C prefer-dynamic` to link `std` statically into `rustc_driver`
+        if let Some(pos) = args.iter().enumerate().position(|(i, a)| {
+            a == "-C" && args.get(i + 1).map(|a| a == "prefer-dynamic").unwrap_or(false)
+        }) {
+            args.remove(pos);
+            args.remove(pos);
+        }
+        if let Some(pos) = args.iter().position(|a| a == "-Cprefer-dynamic") {
+            args.remove(pos);
+        }
+    }
+
     let mut cmd = match env::var_os("RUSTC_WRAPPER_REAL") {
         Some(wrapper) if !wrapper.is_empty() => {
             let mut cmd = Command::new(wrapper);
@@ -99,9 +116,6 @@ fn main() {
     };
     cmd.args(&args).env(dylib_path_var(), env::join_paths(&dylib_path).unwrap());
 
-    // Get the name of the crate we're compiling, if any.
-    let crate_name = parse_value_from_args(&orig_args, "--crate-name");
-
     if let Some(crate_name) = crate_name {
         if let Some(target) = env::var_os("RUSTC_TIME") {
             if target == "all"

src/bootstrap/src/core/build_steps/compile.rs

@@ -1836,7 +1836,12 @@ impl Step for Assemble {
         let src_libdir = builder.sysroot_libdir(build_compiler, host);
         for f in builder.read_dir(&src_libdir) {
             let filename = f.file_name().into_string().unwrap();
-            if (is_dylib(&filename) || is_debug_info(&filename)) && !proc_macros.contains(&filename)
+            let can_be_rustc_dep = filename.starts_with("rustc_driver-")
+                || filename.starts_with("librustc_driver-")
+                || build_compiler.stage == 0;
+            if can_be_rustc_dep
+                && (is_dylib(&filename) || is_debug_info(&filename))
+                && !proc_macros.contains(&filename)
             {
                 builder.copy_link(&f.path(), &rustc_libdir.join(&filename));
             }

src/bootstrap/src/core/builder.rs

@@ -2162,7 +2162,7 @@ impl<'a> Builder<'a> {
         // When we build Rust dylibs they're all intended for intermediate
         // usage, so make sure we pass the -Cprefer-dynamic flag instead of
         // linking all deps statically into the dylib.
-        if matches!(mode, Mode::Std | Mode::Rustc) {
+        if matches!(mode, Mode::Std) {
             rustflags.arg("-Cprefer-dynamic");
         }
 

src/tools/clippy/src/main.rs

@@ -1,3 +1,6 @@
+// We need this feature as it changes `dylib` linking behavior and allows us to link to
+// `rustc_driver`.
+#![feature(rustc_private)]
 // warn on lints, that are included in `rust-lang/rust`s bootstrap
 #![warn(rust_2018_idioms, unused_lifetimes)]
 

src/tools/clippy/tests/compile-test.rs

@@ -1,3 +1,6 @@
+// We need this feature as it changes `dylib` linking behavior and allows us to link to
+// `rustc_driver`.
+#![feature(rustc_private)]
 #![warn(rust_2018_idioms, unused_lifetimes)]
 #![allow(unused_extern_crates)]
 

src/tools/rustdoc/main.rs

@@ -1,3 +1,6 @@
+// We need this feature as it changes `dylib` linking behavior and allows us to link to `rustc_driver`.
+#![feature(rustc_private)]
+
 fn main() {
     rustdoc::main()
 }

src/tools/rustfmt/src/git-rustfmt/main.rs

@@ -1,3 +1,7 @@
+// We need this feature as it changes `dylib` linking behavior and allows us to link to
+// `rustc_driver`.
+#![feature(rustc_private)]
+
 #[macro_use]
 extern crate tracing;